KR20190075574A - Preparation method for super absorbent polymer - Google Patents

Abstract

The present invention relates to a method for producing a super absorbent polymer. According to the production method of the super absorbent polymer of the present invention, it is possible to provide a super absorbent polymer having an improved initial absorption rate. The production method of the present invention includes the steps of forming a hydrogel polymer; grinding after mixing a basic aqueous solution; producing a base resin; and performing a crosslinking reaction at the surface.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a super absorbent polymer,

The present invention relates to a method for producing a superabsorbent resin. More particularly, the present invention relates to a method for producing a superabsorbent resin having an improved initial absorption rate.

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing moisture of about 500 to 1,000 times its own weight. As a result, it is possible to develop a super absorbent polymer (SAM), an absorbent gel Material), and so on. Such a superabsorbent resin has started to be put into practical use as a sanitary article and is currently being used for sanitary articles such as diapers for children and sanitary napkins as well as soil repair agents for horticultural use, index materials for construction and construction, seedling- , And as a material for fomentation and the like.

In most cases, such a superabsorbent resin is widely used in the field of sanitary materials such as diapers and sanitary napkins. For this purpose, it is necessary to exhibit a high absorption capacity for moisture and the like, In addition, there is a need to exhibit excellent permeability by keeping the form well even when the water is absorbed and expanded in volume (swollen).

However, it is known that it is difficult to improve both the water retention capacity (CRC), which is the physical property showing the basic absorption power and the water holding capacity of the superabsorbent resin, and the absorptive capacity under pressure (AUL), which shows the property of holding the moisture absorbed even to the external pressure well . This is because, when the overall cross-link density of the superabsorbent resin is controlled to be low, the hydrophobic ability can be relatively high, but the cross-linking structure becomes poor and the gel strength becomes low and the absorbability under pressure can be lowered. On the other hand, when the cross-linking density is controlled to be high and the absorption ability under pressure is improved, moisture can not easily be absorbed through the dense cross-linking structure, and the basic water-holding ability can be lowered. For the above reasons, there is a limit to providing a superabsorbent resin having both a water-repellent ability and an ability to absorb under pressure.

However, recently, a hygroscopic material such as a diaper or a sanitary napkin is becoming thinner, so that a higher absorption performance is required for a superabsorbent resin. Among them, improvement of the water retention ability and the pressure absorption ability, which are opposite physical properties, and improvement of the liquid permeability are becoming important tasks.

In addition, since the superabsorbent resin applied to sanitary materials such as diapers and sanitary napkins absorbs liquid, the surface of the absorbent resin becomes dewy and can give an uncomfortable feeling. To prevent this, it is required that the superabsorbent resin exhibits a fast initial absorption rate. As the initial absorption rate is faster, the surface is kept dry even after being swollen by the liquid, so that a more comfortable use condition can be maintained.

In order to solve the problems of the prior art as described above, it is an object of the present invention to provide a method of manufacturing a superabsorbent resin having a high initial absorption rate.

In order to achieve the above object, according to an aspect of the present invention,

Polymerizing a monomer composition comprising an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized, a blowing agent, a surfactant, an internal cross-linker, and a polymerization initiator to form a hydrous gel polymer;

Mixing and grinding a basic aqueous solution with the hydrogel polymer;

Drying the pulverized polymer to prepare a base resin; And

Performing a surface cross-linking reaction on the base resin;

And a method of producing a superabsorbent resin.

INDUSTRIAL APPLICABILITY According to the method for producing a superabsorbent resin of the present invention, it is possible to provide a superabsorbent resin having an improved initial absorption rate while exhibiting excellent various absorbent properties.

The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises", "comprising", or "having" are used to designate the presence of stated features, steps, components, or combinations thereof, and are not intended to preclude the presence of one or more other features, Components, or combinations thereof, as a matter of convenience, without departing from the spirit and scope of the invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Hereinafter, a method for producing a superabsorbent resin according to an embodiment of the present invention will be described in detail.

A method of manufacturing a superabsorbent resin according to an embodiment of the present invention includes:

Polymerizing a monomer composition comprising an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized, a blowing agent, a surfactant, an internal cross-linker, and a polymerization initiator to form a hydrous gel polymer; Mixing and grinding a basic aqueous solution with the hydrogel polymer; Drying the pulverized polymer to prepare a base resin; And performing a surface cross-linking reaction on the base resin.

For reference, in the specification of the present invention, "polymer" or "polymer" means that the acrylic acid-based monomer is in a polymerized state, and may cover all moisture content ranges or particle diameter ranges. Among the above polymers, a polymer having a water content (moisture content) of about 40% by weight or more after polymerization and before drying can be referred to as a hydrogel polymer.

The term "base resin" or "base resin powder" refers to a polymer prepared by drying and pulverizing the polymer in the form of a powder before the surface crosslinking step described below.

The hydrogel polymer obtained by the polymerization reaction of the acrylic acid-based monomer is subjected to a process such as drying, crushing, classification, surface crosslinking and the like, and is marketed as a superabsorbent resin which is powdery product.

In recent years, not only the absorption properties such as absorption capacity and liquid permeability but also the degree of maintaining the dryness of the surface in the situation where actual diapers are used have become an important measure of diaper characteristics.

The superabsorbent resin obtained by the production method according to one embodiment of the present invention exhibits excellent absorption performance in terms of physical properties such as water retention capacity, pressure absorption capacity and liquid permeability, and is excellent in initial absorption rate and swollen State can be maintained, leading to the present invention.

In the method for producing a superabsorbent resin according to the present invention, the monomer composition, which is a raw material of the superabsorbent resin, may contain an acrylic acid monomer having an acidic group and at least a part of which is neutralized, a foaming agent, a surfactant, .

This will be described in more detail below.

First, the acrylic acid-based monomer is a compound represented by the following Formula 1:

[Chemical Formula 1]

R ¹ -COOM ¹

In Formula 1,

R ¹ is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

M ¹ is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

Preferably, the acrylic acid-based monomer includes at least one selected from the group consisting of acrylic acid, methacrylic acid, monovalent metal salts thereof, bivalent metal salts, ammonium salts and organic amine salts thereof.

Here, the acrylic acid-based monomer may have an acidic group and at least a part of the acidic group may be neutralized. Preferably, the monomer is partially neutralized with an alkali substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide or the like. At this time, the neutralization degree of the acrylic acid monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization can be adjusted according to the final properties. However, if the degree of neutralization is too high, neutralized monomers may precipitate and polymerization may not be smoothly proceeded. On the other hand, if the degree of neutralization is too low, the absorption capacity of the polymer is greatly lowered, have.

The concentration of the acrylic acid-based monomer may be about 20 to about 60% by weight, preferably about 40 to about 50% by weight, based on the monomer composition including the raw material and the solvent of the superabsorbent resin, It may be an appropriate concentration considering the reaction conditions and the like. However, if the concentration of the monomer is excessively low, the yield of the superabsorbent resin may be low and economical efficiency may be deteriorated. On the other hand, if the concentration is excessively high, a part of the monomer may precipitate or the pulverization efficiency may be low Problems such as the like may occur and the physical properties of the superabsorbent resin may be deteriorated.

The monomer composition of the present invention comprises a blowing agent.

The foaming agent causes foaming during polymerization to form pores in the hydrogel polymer, thereby increasing the surface area.

The foaming agent may be a carbonate foaming agent. Examples of the carbonate foaming agent include sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate calcium bicarbonate, calcium bicarbonate, magnesium bicarbonate, or magnesium carbonate may be used.

The blowing agent may be added in an amount of about 0.01 to about 0.5 parts by weight, or about 0.01 to about 0.3 parts by weight, or about 0.01 to about 0.2 parts by weight based on 100 parts by weight of the acrylic acid monomer. If the amount of the foaming agent used is too large, the pores become too large, the gel strength of the superabsorbent resin lowers and the density becomes low, which may cause problems in distribution and storage. In addition, when the amount is too small, the function as a blowing agent may be insignificant.

The monomer composition of the present invention comprises a surfactant.

The surfactant may serve to uniformly distribute the components in the monomer composition during polymerization and to uniformly distribute the bubbles in the whole area of the polymer while maintaining the shape of the bubbles formed by the foaming agent.

As the surfactant, anionic surfactants may preferably be used.

Examples of anionic surfactants that can be used include sodium dodecyl sulfate, sodium stearate, ammonium lauryl sulfate, sodium lauryl ether sulfate, Sodium myreth sulfate, or alkyl ether sulfate compounds similar thereto. The anionic surfactant that can be used is not limited thereto, but preferably sodium dodecyl sulfate or sodium stearate can be used.

The surfactant may be added in an amount of about 0.001 to about 0.5 part by weight, or about 0.002 to about 0.05 part by weight based on 100 parts by weight of the acrylic acid monomer. If the content of the surfactant is excessively low, it is difficult to achieve an improvement in the absorption rate due to insufficient action as a foam stabilizer. On the other hand, if the content is excessively high, the water retention capacity and absorption rate during polymerization may be rather low.

The monomer composition of the present invention comprises an internal cross-linking agent. Examples of the internal crosslinking agent include a crosslinking agent having at least one functional group capable of reacting with the acrylic acid-based monomer and having at least one ethylenic unsaturated group; Or a crosslinking agent having two or more functional groups capable of reacting with a substituent formed by hydrolysis of a substituent and / or a monomer of the acrylic acid-based monomer may be used.

Specific examples of the internal crosslinking agent include N, N'-methylenebisacrylamide, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol di Butylene diol di (meth) acrylate, butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, hexane diol di (meth) acrylate, Acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerin tri Styrene tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, Lee serine, and it can be used at least one selected from the group consisting of ethylene carbonate.

Such an internal crosslinking agent may be included at a concentration of about 0.01 to about 0.5% by weight based on the monomer composition to crosslink the polymerized polymer.

In the method for producing a superabsorbent resin of the present invention, the polymerization initiator used in polymerization is not particularly limited as long as it is generally used in the production of a superabsorbent resin.

Specifically, as the polymerization initiator, a thermal polymerization initiator or a photopolymerization initiator based on UV irradiation may be used depending on the polymerization method. However, even when the photopolymerization method is employed, a certain amount of heat is generated by irradiation of ultraviolet light or the like, and a certain amount of heat is generated as the polymerization reaction, which is an exothermic reaction, proceeds.

The photopolymerization initiator can be used without limitation in the constitution as long as it is a compound capable of forming a radical by light such as ultraviolet rays.

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal Ketal, acyl phosphine, and alpha-aminoketone may be used. On the other hand, as a specific example of the acylphosphine, a commonly used lucyrin TPO, i.e., 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide can be used . More photoinitiators are well described in Reinhold Schwalm, UV Coatings: Basics, Recent Developments and New Applications (Elsevier 2007), p. 115, and are not limited to the above examples.

The photopolymerization initiator may be included in the monomer composition at a concentration of about 0.01 to about 1.0 wt%. If the concentration of such a photopolymerization initiator is too low, the polymerization rate may be slowed. If the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent resin may be small and the physical properties may become uneven.

As the thermal polymerization initiator, at least one selected from persulfate-based initiators, azo-based initiators, initiators consisting of hydrogen peroxide and ascorbic acid can be used. Specifically, examples of the persulfate-based initiator include sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), ammonium persulfate (NH ₄ ) ₂ S ₂ O ₈ ). Examples of the azo-based initiator include 2, 2-azobis (2-amidinopropane) dihydrochloride, 2 , 2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride, 2- (carbamoyl azo) isobutyronitrile Azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, yl) propane] dihydrochloride, and 4,4-azobis- (4-cyanovaleric acid). A variety of thermal polymerization initiators are well described in the Odian book, Principle of Polymerization (Wiley, 1981), p. 203, and are not limited to the above examples.

In the production method of the present invention, the monomer composition of the superabsorbent resin may further contain additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

Raw materials such as acrylic acid-based monomer, photopolymerization initiator, thermal polymerization initiator, internal cross-linking agent and additive having the above-mentioned acid group and at least part of which is neutralized can be prepared in the form of a monomer composition solution dissolved in a solvent.

The solvent which can be used at this time can be used without limitation of its constitution as long as it can dissolve the above-mentioned components. Examples thereof include water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, Propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol At least one selected from ethyl ether, toluene, xylene, butylolactone, carbitol, methylcellosolve acetate and N, N-dimethylacetamide can be used in combination.

The solvent may be included in the remaining amount of the monomer composition excluding the components described above.

On the other hand, the method of forming a hydrogel polymer by thermal polymerization or photopolymerization of such a monomer composition is not particularly limited as long as it is a commonly used polymerization method.

Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization depending on the polymerization energy source. In general, when thermal polymerization is carried out, it may proceed in a reactor having a stirring axis such as a kneader. In the case where light polymerization is proceeded, The polymerization method described above is merely an example, and the present invention is not limited to the polymerization method described above.

For example, the hydrogel polymer obtained by supplying hot air or heating the reactor to a reactor such as a kneader having an agitating shaft as described above and thermally polymerizing the reactor may be supplied to the reactor outlet The discharged hydrogel polymer may be in the range of a few centimeters to a few millimeters. Specifically, the size of the obtained hydrogel polymer may vary depending on the concentration of the monomer composition to be injected, the injection rate, etc. In general, a hydrogel polymer having a weight average particle diameter of 2 to 50 mm can be obtained.

In addition, when photopolymerization proceeds in a reactor equipped with a movable conveyor belt as described above, the form of the hydrogel polymer that is usually obtained may be a hydrogel polymer on a sheet having a belt width. At this time, the thickness of the polymer sheet varies depending on the concentration of the monomer composition to be injected and the injection rate, but it is preferable to supply the monomer composition so that a polymer in the form of a sheet having a thickness of usually about 0.5 to about 5 cm can be obtained. When the monomer composition is supplied to such an extent that the thickness of the polymer in the sheet is too thin, the production efficiency is low, which is undesirable. When the thickness of the polymer on the sheet exceeds 5 cm, the polymerization reaction occurs evenly over the entire thickness due to the excessively thick thickness I can not.

The normal water content of the hydrogel polymer obtained by this method may be about 40 to about 80 wt%. On the other hand, throughout the present specification, the term "moisture content" means the moisture content of the total functional gelated polymer weight minus the weight of the hydrogel polymer in dry state. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer in the process of raising the temperature of the polymer through infrared heating. At this time, the drying condition is a method of raising the temperature from room temperature to about 180 ° C and then keeping it at 180 ° C, and the total drying time is set to 20 minutes including 5 minutes of the temperature raising step, and water content is measured.

According to the production method of the present invention, the polymerization conditions are adjusted so that the water content of the hydrogel polymer before the coarse pulverization is 40 to 50% by the above-mentioned method, and the process conditions are controlled in the pulverization step described later, It is possible to produce a superabsorbent resin of excellent quality with high initial absorption rate while exhibiting excellent various absorption properties.

Next, a step of pulverizing the obtained hydrogel polymer is carried out. The pulverization can be carried out by first mixing a basic aqueous solution with the hydrous gel polymer, and chopping the hydrogel polymer mixed with the basic aqueous solution.

As described above, when the functional gel polymer is pulverized after mixing with a basic aqueous solution and chopping it in a dry state, the surface of the hydrogel polymer becomes ionic, thereby increasing the hydrophilic property of the hydrogel polymer, have. It was confirmed that the faster absorption rate can be maintained even after the surface cross-linking process, and the superabsorbent resin can exhibit the optimized properties in terms of the absorption rate.

The basic aqueous solution may contain a basic substance having a high ionization degree such as potassium hydroxide (KOH), potassium carbonate (K ₂ CO ₃ ), and sodium hydroxide (NaOH).

The concentration of the basic substance in the basic aqueous solution may be about 0.1 to about 10 M, or about 0.5 to about 8 M. [ If the concentration of the basic aqueous solution is too low, a large amount of water may be required to be added to achieve the above-mentioned effect. If the concentration is too high, the sheet may be considerably sticky and the absorption rate may be lowered. It is preferable to use it at the concentration within the above range.

The basic aqueous solution may be mixed in an amount of about 5 to about 20 parts by weight, preferably about 5 to about 15 parts by weight, more preferably about 10 to about 15 parts by weight based on 100 parts by weight of the hydrogel polymer. If the addition amount of the basic aqueous solution is too small, the effect of improving the absorption rate hardly occurs. If too much is added, the hydrogel may become sticky.

Next, the step of drying the pulverized polymer through the above-mentioned pulverizing step is carried out.

The drying temperature of the drying step may be about 150 to about 250 ° C. If the drying temperature is lower than 150 ° C, the drying time becomes excessively long and the physical properties of the superabsorbent resin to be finally formed may deteriorate. When the drying temperature exceeds 250 ° C, only the polymer surface is excessively dried, And the physical properties of the finally formed superabsorbent resin may be deteriorated. Thus, preferably, the drying can proceed at a temperature of from about 150 to about 200 < 0 > C, more preferably from about 160 to about 180 < 0 > C.

On the other hand, in the case of drying time, it may proceed for about 20 to about 90 minutes, but is not limited thereto, considering process efficiency and the like.

The drying method in the drying step may be selected and used as long as it is usually used as a drying step of the hydrogel polymer. Specifically, the drying step can be carried out by hot air supply, infrared irradiation, microwave irradiation, ultraviolet irradiation, or the like. The water content of the polymer after such a drying step may be from about 0.1 to about 10% by weight.

Next, a step of pulverizing the dried polymer obtained through such a drying step into a powder form is carried out.

The polymer powder obtained after the milling step may have a particle diameter of from about 150 to about 850 탆. The pulverizer used for crushing with such a particle size is specifically a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, A jog mill, or the like may be used, but the present invention is not limited to the above examples.

In order to control the physical properties of the superabsorbent resin powder which is finally produced after the pulverization step, a separate process of classifying the polymer powder obtained after the pulverization according to the particle size may be carried out. . ≪ / RTI >

Next, the surface cross-linking reaction step is performed on the polymer obtained as described above, that is, the base resin to perform the surface cross-linking reaction step for the ground polymer.

In a general method of producing a superabsorbent resin, a surface cross-linking solution containing a surface cross-linking agent is mixed with a dried and ground polymer, that is, a base resin, and then the surface cross-linking reaction .

The surface crosslinking step is a step of inducing a crosslinking reaction on the surface of the pulverized polymer in the presence of a surface crosslinking agent to form a superabsorbent resin having improved physical properties. Through such surface crosslinking, a surface crosslinked layer (surface modifying layer) is formed on the surface of the pulverized polymer particles.

Generally, the surface cross-linking agent is applied to the surface of the superabsorbent resin particles, so that the surface cross-linking reaction occurs on the surface of the superabsorbent resin particles, which improves the crosslinkability on the surface of the particles without substantially affecting the inside of the particles. Thus, the surface cross-linked superabsorbent resin particles have a higher degree of crosslinking in the vicinity of the surface than in the interior.

The surface cross-linking agent is not limited in its composition as long as it is a compound capable of reacting with a functional group contained in the polymer.

Preferably, in order to improve the properties of the resulting superabsorbent resin, a polyhydric alcohol compound as the surface crosslinking agent; Epoxy compounds; Polyamine compounds; Halo epoxy compounds; A condensation product of a haloepoxy compound; Oxazoline compounds; Mono-, di- or polyoxazolidinone compounds; Cyclic urea compounds; Polyvalent metal salts; And an alkylene carbonate compound can be used.

Specific examples of the polyhydric alcohol compound include mono-, di-, tri-, tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl- - pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,2-cyclohexane dimethanol, and the like.

Examples of the epoxy compounds include ethylene glycol diglycidyl ether and glycidol. Examples of the polyamine compounds include ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentaamine, pentaethylene hexamine , Polyethyleneimine, and polyamide polyamines can be used.

As the haloepoxy compound, epichlorohydrin, epibromohydrin, and? -Methyl epichlorohydrin may be used. On the other hand, as the mono-, di- or polyoxazolidinone compounds, for example, 2-oxazolidinone and the like can be used.

As the alkylene carbonate compound, ethylene carbonate and the like can be used. These may be used alone or in combination with each other. On the other hand, in order to increase the efficiency of the surface cross-linking step, at least one polyhydric alcohol compound having 2 to 10 carbon atoms among these surface cross-linking agents may be used.

The amount of the surface crosslinking agent to be added may be appropriately selected depending on the kind of the surface crosslinking agent to be added and the reaction conditions, but is usually about 0.001 to about 5 parts by weight, preferably about 0.01 to about 5 parts by weight, About 3 parts by weight, more preferably about 0.05 to about 2 parts by weight may be used.

If the content of the surface cross-linking agent is too small, surface cross-linking reaction hardly occurs. If the amount of the surface cross-linking agent is more than 5 parts by weight based on 100 parts by weight of the polymer, excessive absorption of the surface cross- .

On the other hand, the surface cross-linking reaction step may include a method of mixing the surface cross-linking agent and the pulverized polymer into a reaction tank and mixing them, a method of spraying a surface cross-linking agent on the pulverized polymer, a method of continuously spraying the pulverized polymer and surface cross- A method of supplying and mixing them, and the like.

The surface cross-linking reaction step may be carried out at a temperature of 100 to 250 ° C. The surface cross-linking reaction may be conducted for 1 minute to 120 minutes, preferably 1 minute to 100 minutes, more preferably 10 minutes to 60 minutes. That is, the surface cross-linking reaction step may be carried out under the above-mentioned conditions in order to prevent the polymer particles from being damaged due to excessive reaction while inducing minimal surface cross-linking reaction.

The superabsorbent resin produced by the production method of the present invention can have a fast initial absorption rate without lowering physical properties such as water retention capacity and pressure absorption capacity.

For example, the superabsorbent resin prepared by the above process may have a retention capacity (CRC) of at least about 27 g / g, or at least about 29 g / g, or at least about 30 g / g, measured according to EDANA method WSP 241.3 Or less, about 40 g / g or less, or about 38 g / g or less, or about 35 g / g or less.

In addition, the superabsorbent resin produced by the above production method may have a vortex time of 30 seconds or less, or about 25 seconds or less, or about 22 seconds or less. The lower the absorbing rate, the better the lowering of the absorbing rate is theoretically 0 seconds, for example about 5 seconds or more, about 10 seconds or more, or about 12 seconds or more.

The absorption rate refers to a time (unit: sec) in which a vortex of a liquid disappears due to rapid absorption when a superabsorbent resin is added to physiological saline and stirred. When the time is shorter, Can be seen to have a fast initial absorption rate.

When 1 g of the superabsorbent resin is immersed in 2 L of tap water and swelled for 1 minute, the water absorption capacity for one minute defined as the weight of water absorbed in the superabsorbent resin is 100 g or more, or 110 g or more, or 120 g Or more and 200 g or less, or 190 g or less, or 180 g or less.

The tap water used in the physical property evaluation has an electrical conductivity of 170 to 180 μS / cm. Since the electrical conductivity of the tap water greatly affects the properties of the tap water, it is necessary to use tap water having an equivalent level of electrical conductivity to measure the physical properties.

Further, when 1 g of the superabsorbent resin is immersed in 150 ml of saline (0.9 wt% NaCl aqueous solution) and swelled for 1 minute, the absorption capacity of 1 minute brine is defined as the weight of the brine absorbed into the superabsorbent resin for 25 minutes or more, Or 30 g or more, or 35 g or more, 100 g or less, or 90 g or less, or 80 g or less.

As described above, the superabsorbent resin of the present invention can provide a high quality hygiene material having an excellent absorbing ability, especially a high initial absorption rate.

The present invention will be described in more detail in the following Examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

EXAMPLES -

Preparation of superabsorbent resin

Example 1

1.5 g of polyethylene glycol diacrylate (PEGDA, Mw = 523) as a crosslinking agent and 0.04 g of diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide as a photoinitiator were added to 500 g of acrylic acid Was added and dissolved. Another vessel was mixed with 640 g of 31.5% caustic soda (NaOH) and 170 g of water and stirred. After 30 minutes, caustic soda (NaOH) and water aqueous solution were mixed with acrylic acid mixed solution using a pump vessel. When the temperature is lowered to 45 ° C after the temperature has risen, the mixture is mixed with 0.4 g of a thermal initiator, sodium persulfate (SPS), 0.9 g of sodium bicarbonate as a blowing agent, sodium dodecyl sulfate as a surfactant 0.0 > g < / RTI > sulfate). This aqueous solution was added to a container made of stainless steel having a width of 250 mm, a length of 250 mm and a height of 30 mm, irradiated with ultraviolet light (irradiation amount: 10 mV / cm ² ), subjected to UV polymerization for 60 seconds and heated for 120 seconds to obtain a hydrogel polymer . The obtained hydrogel polymer was pulverized into a size of 2 mm * 2 mm, and the water content was measured and found to be 40.1%.

200 g of potassium hydroxide aqueous solution (0.5M concentration KOH) was added to 1400 g of pulverized hydrogel polymer and chopped. 1000 g of the obtained gel resin was spread on a stainless wire gauze having a hole size of 600 mu m to a thickness of about 30 mm, And dried for 30 minutes. The dry polymer thus obtained was pulverized using a pulverizer and classified with a standard mesh of ASTM standard to obtain a base resin having a particle size of 150 to 850 탆.

A surface cross-linking solution containing 1 part by weight of ethylene carbonate, 4 parts by weight of water and 0.02 part by weight of silica was sprayed onto 100 parts by weight of the base resin and mixed in a container made of a stirrer and a double jacket. . Then, the surface-treated powder was classified into a standard mesh of ASTM standard to obtain a superabsorbent resin powder having a particle size of 150 to 850 탆.

Example 2

In Example 1, a superabsorbent resin was prepared in the same manner as in Example 1, except that 200 g of an aqueous solution of potassium hydroxide (1.5M concentration KOH) was added during the grinding of the hydrogel polymer.

Example 3

In Example 1, a superabsorbent resin was prepared in the same manner as in Example 1, except that 200 g of aqueous potassium hydroxide solution (2.5M concentration KOH) was added during the grinding of the hydrogel polymer.

Example 4

In Example 1, a superabsorbent resin was prepared in the same manner as in Example 1, except that 200 g of aqueous potassium hydroxide solution (5M concentration KOH) was added during the pulverization of the hydrogel-like polymer.

Example 5

A superabsorbent resin was prepared in the same manner as in Example 1, except that 200 g of potassium hydroxide aqueous solution (7.5 M concentration KOH) was added during grinding of the hydrogel polymer in Example 1.

Example 6

In Example 1, a superabsorbent resin was prepared in the same manner as in Example 1, except that 200 g of potassium carbonate aqueous solution (0.5M concentration K ₂ CO ₃ ) was added during pulverization of the hydrogel polymer.

Example 7

In Example 1, a superabsorbent resin was prepared in the same manner as in Example 1, except that 200 g of an aqueous potassium carbonate solution (1.5M concentration K ₂ CO ₃ ) was added during pulverization of the hydrogel polymer.

Example 8

In Example 1, a superabsorbent resin was prepared in the same manner as in Example 1, except that 200 g of an aqueous potassium carbonate solution (2.5 M concentration K ₂ CO ₃ ) was added during the pulverization of the hydrogel polymer.

Example 9

In Example 1, a superabsorbent resin was prepared in the same manner as in Example 1, except that 200 g of an aqueous potassium carbonate solution (5M concentration K ₂ CO ₃ ) was added during the grinding of the hydrogel-like polymer.

Example 10

In Example 1, a superabsorbent resin was prepared in the same manner as in Example 1, except that 200 g of potassium carbonate aqueous solution (7.5M concentration K ₂ CO ₃ ) was added during pulverization of the hydrogel polymer.

Comparative Example 1

In Example 1, a superabsorbent resin was prepared in the same manner as in Example 1, except that no basic aqueous solution was added during the pulverization of the hydrogel polymer.

<Experimental Example>

The properties of the superabsorbent resin prepared in the above Examples and Comparative Examples were evaluated by the following methods.

Unless otherwise indicated, all of the following physical properties were evaluated at room temperature (25 캜), and physiological saline or brine means 0.9% by weight sodium chloride (NaCl) aqueous solution.

(1) Centrifuge Retention Capacity (CRC)

The retention capacity of each resin by the zero-load capacity was measured according to EDANA WSP 241.3.

Specifically, a superabsorbent resin W ₀ (g) (about 0.2 g) was uniformly put in an envelope made of a nonwoven fabric and sealed, and then immersed in physiological saline (0.9 wt%) at room temperature. After 30 minutes, water was drained from the envelope for 3 minutes under a condition of 250 G using a centrifuge, and the mass W ₂ (g) of the envelope was measured. Further, after the same operation was performed without using a resin, the mass W ₁ (g) at that time was measured. Using the obtained masses, CRC (g / g) was calculated according to the following equation.

[Equation 1]

CRC (g / g) = {[W ₂ (g) - W ₁ (g)] / W ₀ (g)

(2) Vortex time

The vortex time was measured in seconds according to the method described in International Patent Application No. 1987-003208.

Specifically, 2 g of superabsorbent resin was added to 50 mL of physiological saline at 23 to 24 DEG C, and the magnetic bar (diameter 8 mm, length 30 mm) was stirred at 600 rpm until the disappearance of the vortex Was measured in seconds.

 (3) 1 minute Water absorption capacity

① 1 g of superabsorbent resin was put into a tea bag of 15 cm in width and 30 cm in length, and 2 L of tap water was poured, followed by swelling for 1 minute.

② After swelling for 1 minute, lift the tea bag containing the superabsorbent resin out of the tap water. After 1 minute has elapsed, measure the weight of the tea bag and the superabsorbent resin that have lost water, and subtract the weight of the empty tea bag 1-minute water-absorption ability.

In this case, the water conductivity was measured using Orion Star A222 (company: Thermo Scientific) with an electrical conductivity of 170 to 180 μS / cm.

(4) 1-minute salt water absorption capacity

① 1 g of superabsorbent resin was put into a 200 ml beaker, and 150 ml of brine was poured, followed by swelling for 1 minute.

(2) A superabsorbent resin swollen in a circular sieve having an inner diameter of 8 cm of 100 mesh was placed and the salt water was drained for 1 minute. this? The brine discharged was collected in another beaker.

③ In 150 ml of brine, we subtract the weight of brine discharged from the superabsorbent resin for one minute at ② and calculate it for 1 minute of salt water absorption capacity.

The physical properties of the above examples and comparative examples are shown in Table 1 below.

Base resin High absorbency resin (after surface cross-linking) CRC
(g / g) Number of minutes
Absorption capacity
(g) Vortex time
(sec) CRC
(g / g) 1 minute
Water supply
Absorption capacity
(g) 1 minute
Brine
Absorption capacity
(g) Vortex time
(sec) Example 1 36.4 142 27 27.1 138 31 22 Example 2 35.8 152 26 27.9 140 34 21 Example 3 35.1 174 26 28.5 162 52 18 Example 4 35.3 168 24 30.2 151 46 19 Example 5 36.5 160 25 31.0 141 40 19 Example 6 36.8 138 24 31.2 130 31 21 Example 7 37.0 145 26 30.8 134 35 23 Example 8 37.2 160 26 30.7 158 44 22 Example 9 37.7 148 27 30.8 131 34 24 Example 10 37.7 139 26 31.0 126 31 25 Comparative Example 1 36.1 92 47 32.1 88 22 38

Referring to Table 1, it was confirmed that the embodiments of the present invention exhibited a fast absorption rate both in the measurement by the vortex method and in the measurement of water / saline water absorption capacity per minute.

On the other hand, the comparative example shows that the initial absorption rate, which is evaluated by the one-minute tap water absorption capacity and the one-minute tap water absorption capacity, and the absorption rate by the vortex method are both lower than those of the examples.

Claims (11)

Polymerizing a monomer composition comprising an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized, a blowing agent, a surfactant, an internal cross-linker, and a polymerization initiator to form a hydrous gel polymer;
Mixing and grinding a basic aqueous solution with the hydrogel polymer;
Drying the pulverized polymer to prepare a base resin; And
Performing a surface cross-linking reaction on the base resin;
Absorbent resin.
The method according to claim 1,
The foaming agent may be selected from the group consisting of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium bicarbonate, magnesium bicarbonate, Magnesium bicarbonate, and magnesium carbonate. The method for producing a superabsorbent resin according to claim 1,
The method according to claim 1,
The foaming agent is added in an amount of 0.01 to 0.5 parts by weight per 100 parts by weight of the acrylic acid monomer By weight based on the weight of the resin.
The method according to claim 1,
The surfactant may be selected from the group consisting of sodium dodecyl sulfate, sodium stearate, ammonium lauryl sulfate, sodium lauryl ether sulfate, and sodium missesulfate sodium myreth sulfate). &lt; / RTI &gt;
The method according to claim 1,
Wherein the surfactant is contained in an amount of 0.001 to 0.5 part by weight based on 100 parts by weight of the acrylic acid monomer.
The method according to claim 1,
Wherein the basic aqueous solution comprises at least one basic substance selected from the group consisting of potassium hydroxide (KOH), potassium carbonate (K ₂ CO ₃ ), and sodium hydroxide (NaOH).
The method according to claim 1,
Wherein a concentration of the basic substance in the basic aqueous solution is 0.1 to 10 M.
The method according to claim 1,
Wherein the basic aqueous solution is added in an amount of 5 to 20 parts by weight based on 100 parts by weight of the hydrogel-based polymer.
The method according to claim 1,
Wherein the superabsorbent resin has a water absorption capacity of 1 g or more defined as the weight of water absorbed by the superabsorbent resin for 1 minute when 1 g of the superabsorbent resin is immersed in 2 L of tap water and swelled for 1 minute, A method for producing a resin.
The method according to claim 1,
The superabsorbent resin has a 1-minute salt water absorption capacity defined by the weight of the brine absorbed by the superabsorbent resin for 1 minute when 1 g of the superabsorbent resin is immersed in 150 ml of saline (0.9 wt% NaCl aqueous solution) Is 25 g or more.
The method according to claim 1,
Wherein the superabsorbent resin has an absorption rate (vortex time) of 30 seconds or less.